The 10th International Symposium on Sturgeon (ISS10)

As part of the ongoing conservation and reintroduction program of the Baltic sturgeon (Acipenser oxyrinchus), a species regionally extinct, the preferential habitats and potential aggregation spots are identified, intra-specific variability in movement behavior is assessed, and interactions with anthropogenic impacts (dredge sites, fishing gear) are to be evaluated.
A total of 74 individuals were monitored over several weeks using a combination of active and passive telemetry: 25 individuals (average FL = 305 mm) released in winter 2024 and 49 individuals (average FL = 829 mm) released in summer 2025. Monitoring extended. The data acquired were complemented by catch-reports from local fishermen. Habitat characteristics were assessed through river mapping using a side-scan sonar (Hummingbird Solix 12).
Three main behavioral patterns were identified: (i) fast movers, migrating downstream within a few days; (ii) residents, remaining in localized habitats for extended periods; and (iii) explorers, repeatedly moving upstream and downstream in a 40 km range. Aggregation behavior was inconsistent, with no stable group movements detected. In total, 4% and 25% of tagged individuals were captured in fishing gear, primarily gillnets, in winter and spring respectively.
The preliminary results highlight pronounced intra-specific variability in movement strategies, emphasizing the need to account for different behavioral profiles in conservation planning. Maintaining and protecting suitable habitats along the Oder River is crucial to accommodate both mobile and resident individuals. Habitat-focused management, combined with measures to reduce risks from fishing fatalities, will be key to supporting the long-term success of Baltic sturgeon restoration.
 

telemetry,intra-specific variability,habitat use,Acipenser oxyrinchus,migration behaviors